The present invention is directed to vertebral stabilization of a spine using one or more rods anchored into the vertebrae.
Back pain is one of the most common and often debilitating conditions affecting millions of people in all walks of life. Today, it is estimated that over ten million people in the United States alone suffer from persistent back pain. Approximately half of those suffering from persistent back pain are afflicted with chronic disabling pain, which seriously compromises a person's quality of life and is the second most common cause of worker absenteeism. Further, the cost of treating chronic back pain is very high, even though the majority of sufferers do not receive treatment due to health risks, limited treatment options and inadequate therapeutic results. Thus, chronic back pain has a significantly adverse effect on a person's quality of life, on industrial productivity, and on heath care expenditures.
Degenerative spinal column diseases, such as disc degenerative diseases (DDD), spinal stenosis, spondylolisthesis, and so on, need surgical operation if they do not respond to conservative treatment.
Various methods of spinal immobilization have been known and used during this century in the treatment of spinal instability and displacement. One treatment for spinal stabilization is immobilization of the joint by surgical fusion, or arthrodesis. This method has been known since its development in 1911 by Hibbs and Albee. However, in many cases, and in particular, in cases involving fusion across the lumbosacral articulation and when there are many levels involved, pseudoarthrosis is a problem. It was discovered that immediate immobilization was necessary in order to allow a bony union to form.
Typically, spinal decompression is the first surgical procedure that is performed. The primary purpose of decompression is to reduce pressure in the spinal canal and on nerve roots located therein by removing a certain tissue of the spinal column to reduce or eliminate the pressure and pain caused by the pressure. If the tissue of the spinal column is removed the pain is reduced but the spinal column is weakened. Therefore, fusion surgery (e.g., ALIF, PLIF or posterolateral fusion) is often necessary for spinal stability following the decompression procedure. However, following the surgical procedure, fusion takes additional time to achieve maximum stability and a spinal fixation device is typically used to support the spinal column until a desired level of fusion is achieved. Depending on a patient's particular circumstances and condition, a spinal fixation surgery can sometimes be performed immediately following decompression, without performing the fusion procedure. The fixation surgery is performed in most cases because it provides immediate postoperative stability and, if fusion surgery has also been performed, it provides support of the spine until sufficient fusion and stability has been achieved.
Internal fixation refers to therapeutic methods of stabilization which are wholly internal to the patient. External fixation in contrast involves at least some portion of the stabilization device which is external to the patient's body. Internal fixation is advantageous since the patient is allowed greater freedom with the elimination of the external portion of the device and the possibility of infections, such as pin tract infection, is reduced.
Conventional methods and apparatus for vertebral stabilization and/or fusion involve fixing a rod between adjacent vertebrae to prevent motion therebetween. Usually, more than one rod is utilized in a posterior, bilateral configuration with respect to the spinous process. Respective pedicle screws are inserted into the pedicles of the vertebrae through the facets thereof such that the tulips of the screws may fuse to the vertebrae. A rod is fixed to a pair of tulips in order to fix the relative motion between the adjacent vertebrae. Multi-level fusion may be achieved by utilizing more than two pedicle screws on each side of the spinous process and fixing a rod to all of the respective screws. The surgery may require an incision of approximately 60-80 mm longitudinally along the posterior of the spine and peeling back the muscle on each side of the spinous process to expose the facets and pedicles of the adjacent vertebrae.
This surgery is significantly invasive because it involves trauma to the skin, fat, and particularly the muscle. As it requires a significant period of time to heal the muscle and achieve at least partial elasticity thereof, in at least some patients it is not desirable to traumatize muscle.
Other techniques have been developed to reduce the trauma to the muscle during surgery as described in U.S. Pat. No. 6,530,929 and U.S. patent application No. 2002/0161368, the entire disclosures of which are hereby incorporated by reference in their entirety. These publications disclose making three “stub incisions” on each side of the spinous process to accommodate insertion of a rod/pedicle screw assembly. The first and second stub incisions are made adjacent to the respective vertebrae and the third incision is made longitudinally offset from the other two incisions. Each incision is dilated and respective tubes are inserted into the incisions such that they extend from the skin through the muscle to the respective pedicles of the adjacent vertebrae. Screws are then passed through the tubes and inserted into the respective pedicles. A special instrument is then utilized to shape the rod. The instrument is also utilized to insert the rod through the third incision and navigate the rod longitudinally through the muscle from the third incision to the second and first incisions such that the rod passes through respective tulips of each screw. The rod may then be fixed to the respective screws.
While this technique reduces the trauma to the skin and muscle as compared with the aforementioned surgical technique, it still results in a significant amount of trauma to the muscle as the rod is forced through and along the muscle when traveling from the third incision to each of the second and first incisions.
Therefore, conventional spinal fixation devices and surgical techniques have not provided a satisfactory solution to the problems associated with spinal fixation surgery, particularly with respect to minimizing muscle trauma and the size, length and number of surgical incisions required.